Palsa Research Articles

A study of palsa bog organic matter stabilization in response to holocene climate change using 13C NMR and FTICR MS

Spiders have been collected by pitfall traps from two palsa bogs in the vicinity of Vardø in Finnmark, northern Norway. A total of 449 specimens belonging to 27 species from 4 families were caught. Two major ecological guilds were present, active vagrant forms, mainly consisting of lycosids, and the smaller net-building species represented by Linyphiidae and Hahniidae. Linyphiids made up 70% of the species but only 38% of the individuals, the lycosids being most abundant. Faunal differences between sites is probably caused by placement of the traps in different parts of the bogs. Seven species are new to Finnmark, although one has been reported before without being named. General faunistic and taxonomic comments are given on a few additional species: Agyneta mossica, recently reported from Norway, Agyneta sp., Arctosa alpigena lamperti, and Ozyptila arctica.

Palsa bogs are carbon sinks and help preserve permafrost in northern regions. However, under the influence of climate warming and permafrost thawing in peatlands, changes in their biogeochemical properties occur. Using the example of three sections made on the territory of the Numto Natural Park (KhMAO-Yugra), where the permafrost is extremely unstable, the distribution patterns of elements in the peat deposit profiles were determined. Determination of trace elements in the samples was carried out using mass spectral and atomic emission spectroscopy methods (ICP–MS and ICP–OES). The peat of the study area is characterized by low ash content. An increased content of Fe, Mn, and Cr was noted, which is typical for the peat of Western Siberia. The concentration of heavy metals traditionally considered as indicators of technogenic pollution (Cd, Pb, Cr, Ni, Cu) in peat is low due to the remoteness from the sources of technogenesis. The intraprofile distribution of metals is influenced by the botanical composition of peat. Dwarfshrub peat, compared to Sphagnum peat, has a higher content of Pb, Cu and Cd.

West Siberian mires covering more than 50% of area in the subarctic are still poorly investigated despite their thick peat sediments suitable for paleogeographic research of past long-term landscape and climatic changes. In this research, a combination of paleoecological methods were used, including the analysis of pollen, spores, diatoms, NPPs, and macrofossils, the measurement of peat humification, and quantitative paleoclimate reconstruction. This multi-proxy approach was applied to study a palsa bog (frost peat heave mound) located in the north of western Siberia on the border of the northern taiga and forest–tundra (65°18′56″ N, 72°52′27″ E). Chronology is based on 21 radiocarbon dates, which were calibrated in CLAM. Studies have shown that sediments of palsa bog Nadym of a 1050 cm thickness were formed both in the Holocene and earlier periods of the Quaternary. Radiocarbon dating worked well for peat sequences (610 cm thick), but failed for underlying lacustrine and mineral sediments (440 cm thick). Numerous remains of salt-water diatoms and exotic Neogene pollen were found in the lacustrine sediments (650–850 cm). The oldest sediments (850–1050 cm) have signs of secondary epicryogenic diagenesis in the form of cryogenic iron-enriched granules. Both lacustrine and bottom sediments contain abundant coniferous pollen. At the same time, spore–pollen complexes dated to the Last Glacial Age were not found in low sediments because of failed dates. To explain this, the authors turn to the hypothesis of glyacioisostatic compensation, according to which the study area was uplifted during the Last Glacial Age and the ancient deposits underwent secondary diagenesis in subaerial conditions. Holocene lacustrine sedimentation began to form about 9800 cal. a BP. These lacustrine sediments turned out to be enriched in redeposited Neogene pollen and diatoms. It was interpreted as an influence of excess humid climate in combination with geological subsidence of landscape in the study area during the Early Holocene. This caused lake formation and introduction of exotic microfossils via surface run-off from higher-relief areas in the catchment. Syngenetic sedimentation in the Nadym section is associated only with peat-mire deposits covering the last 8400 cal. a BP. For this time, the dynamic of vegetation cover and quantitative changes in paleoclimate were reconstructed using spore–pollen, macrofossil, humus, and NPP data as well as the information–statistical method of V.A. Klimanov. The spore–pollen analysis revealed four main phases in the development of vegetation cover: 1. Spruce–birch forests with open meadows and lakes (8400–7600 cal. a BP); 2. Dominance of spruce forests and thawed eutrophic (minerotrophic) mires (7600 to 6500 cal. a BP); 3. Coniferous–birch forests and thawed mesotrophic mires (6500 to 4500 cal. a BP); 4. Birch–pine forests and oligotrophic (ombrotrophic) bogs with permafrost mounds—palsa bogs (approx. the last 4500 years). Quantitative reconstructions of paleoclimate based on pollen data show that in most cases the periods of a sharp decrease in mean January and mean July temperatures coincided with episodes of low solar activity. The assumption was made about the determining influence of solar activity on the formation of permafrost in the soils and mires of the study area. Sun minima caused permafrost formation in the mire periodically since 8400 cal. a BP in study peatland, but complete freezing of the peat mire and formation of the palsa bog occurred at c. 2800 cal. a BP.

The study area in the north of Western Siberia is located in the southern tundra–taiga ecotone near the southern boundary of discontinuous permafrost zone. Three contrasting ecosystems—pine forests with Albic Podzols; palsa with Histic Oxyaquic Turbic Cryosols, and bogs with Fibric Histosols—predominate in this area. The objectives of the study included evaluation of the CO2 emission from soils in the growing seasons of 2019–2022 and analysis of the factors controlling spatial and interannual variability of the emission. The study included analysis of the soil respiration (static closed chamber method) data and soil hydrothermal parameters in August for four years. In the absence of definite trends in climatic parameters over the past 10 years, a gradual increase in the soil temperature in all ecosystems and an increase in the depth of summer thawing in palsa were observed. These changes were not accompanied by significant changes in the CO2 emission. Its averaged values varied from 485 to 540 mg CO2/(m2 h) in forest ecosystems and from 150 to 255 mg CO2/(m2 h) in the palsa–bog complex with high coefficients of spatial variability. High CO2 emission in forest ecosystems is determined by a favorable hydrothermal regime, high root biomass, and good water-physical properties. Part of the CO2 produced by palsa soils is transported with suprapermafrost water flows toward the adjacent bog and is released from the surface of bog soils. Soil temperature interrelated with seasonal thawing depth proved to be a significant predictor of the spatial variability of CO2 emission from the soils of the palsa–bog complex.

Растительность торфяных бугров болотных комплексов севера Западной Сибири и полуострова Таймыр

Melting permafrost mounds in subarctic palsa mires are thawing under climate warming and have become a substantial source of N2O emissions. However, mechanistic insights into the permafrost thaw-induced N2O emissions in these unique habitats remain elusive. We demonstrated that N2O emission potential in palsa bogs was driven by the bacterial residents of two dominant Sphagnum mosses especially of Sphagnum capillifolium (SC) in the subarctic palsa bog, which responded to endogenous and exogenous Sphagnum factors such as secondary metabolites, nitrogen and carbon sources, temperature, and pH. SC's high N2O emission activity was linked with two classes of distinctive hyperactive N2O emitters, including Pseudomonas sp. and Enterobacteriaceae bacteria, whose hyperactive N2O emitting capability was characterized to be dominantly pH-responsive. As the nosZ gene-harboring emitter, Pseudomonas sp. SC-H2 reached a high level of N2O emissions that increased significantly with increasing pH. For emitters lacking the nosZ gene, an Enterobacteriaceae bacterium SC-L1 was more adaptive to natural acidic conditions, and N2O emissions also increased with pH. Our study revealed previously unknown hyperactive N2O emitters in Sphagnum capillifolium found in melting palsa mound environments, and provided novel insights into SC-associated N2O emissions.

Silicon enhancement for endorsement of Xanthomonas albilineans infection in sugarcane

Температурный режим торфяной залежи бугров и топей плоскобугристых болотных комплексов Западной Сибири

Active processes of permafrost thaw in Western Siberia increase the number of soil subsidencies, thermokarst lakes and thaw ponds. In continuous permafrost zones, this process promotes soil carbon mobilisation to water reservoirs, as well as organic matter (OM) biodegradation, which produces a permanent flux of carbon dioxide (CO2) to the atmosphere. At the same time, the biogeochemical evolution of aquatic ecosystems situated in the transition zone between continuous permafrost and permafrost-free terrain remains poorly known. In order to better understand the biogeochemical processes that occur in thaw ponds and lakes located in discontinuous permafrost zones, we studied ~30 small (1–100,000 m2) shallow (<1 m depth) lakes and ponds formed as a result of permafrost subsidence and thaw of the palsa bog located in the transition zone between the tundra and forest-tundra (central part of Western Siberia). There is a significant increase in dissolved CO2 and methane (CH4) concentration with decreasing water body surface area, with the largest supersaturation with respect to atmospheric CO2 and CH4 in small (<100 m2) permafrost depressions filled with thaw water. Dissolved organic carbon (DOC), conductivity, and metal concentrations also progressively increase from large lakes to thaw ponds and depressions. As such, small water bodies with surface areas of 1–100 m2 that are not accounted for in the existing lake and pond databases may significantly contribute to CO2 and CH4 fluxes to the atmosphere, as well as to the stocks of dissolved trace elements and organic carbon. In situ lake water incubation experiments yielded negligible primary productivity but significant oxygen consumption linked to the mineralisation rate of dissolved OM by heterotrophic bacterioplankton, which produce a net CO2 flux to the atmosphere of 5 ± 2.5 mol C m2 year−1. The most significant result of this study, which has long-term consequences on our prediction of aquatic ecosystem development in the course of permafrost degradation is CO2, CH4, and DOC concentrations increase with decreasing lake age and size. As a consequence, upon future permafrost thaw, the increase in the number of small water bodies, accompanied by the drainage of large thermokarst lakes to the hydrological network, will likely favour (i) the increase of DOC and colloidal metal stocks in surface aquatic systems, and (ii) the enhancement of CO2 and CH4 fluxes from the water surface to the atmosphere. According to a conservative estimation that considers that the total area occupied by water bodies in Western Siberia will not change, this increase in stocks and fluxes could be as high as a factor of ten.

В августе 2011 г. в подзоне южной тундры Западной Сибири ( ключевой участок « Ямбург», 67.97° с.ш., 75.4° в.д. ) были проведены измерения удельного потока СН 4 статическим камерным методом из мерзлых плоскобугристых болот. Несмотря на то, что мерзлотные бугры являются вторым по распространённости типом болотных микроландшафтов в тундровой зоне Западной Сибири, данных о величине эмиссии метана из них до сих пор крайне недостаточно. Среднее значение удельного потока метана из мерзлых бугров тундры Западной Сибири составило 0.13 ± 0.29 мг C -СН 4·м -2·час -1. Полученные результаты были использованы в рамках развиваемого авторами подхода к вычислению регионального потока метана – стандартной модели, а именно её новой версии Вс9. Оказалось, что несмотря на распространённость в зоне тундры Западной Сибири, мерзлотные бугры выделяют в атмосферу лишь 1.9 килотонны С-СН 4·год -1 ( 2% от потока с болот тундры ). Вычисленный поток с территории всех болот западносибирской тундры оказался равным около 108.7 килотонн С-СН 4 в год, что соответствует примерно 4% региональной эмиссии метана из всех болот Западной Сибири. Проводится попытка оценить репрезентативность как уже опубликованных, так и публикуемых в настоящей статье данных об эмиссии метана из болот в зоне тундры Западной Сибири, полученных в течение летнее-осенних периодов 2009-2011 гг.

Pingos, palsas and lithalsas comparison with the Martian mounds

Stability of palsa at the southern margin of its distribution on the Kola Peninsula

The Holocene development of a treed palsa bog and a peat plateau bog, located near the railroad to Churchill in the Hudson Bay Lowlands of northeastern Manitoba, was traced using peat macrofossil and radiocarbon analyses. Both sites first developed as wet rich fens through paludification of forested uplands around 6800 cal. yr BP. Results show a 20th‐century age for the palsa formation and repeated periods of permafrost aggradation and collapse at the peat plateau site during the late Holocene. This timing of permafrost dynamics corroborates well with that inferred from previous studies on other permafrost peatlands in the same region. The developmental history of the palsa and peat plateau bogs is similar to that of adjacent permafrost‐free fens, except for the specific frost heave and collapse features associated with permafrost dynamics. Permafrost aggradation and degradation is ascribed to regional climatic, local autogenic and other factors. Particularly the very recent palsa development can be assessed in terms of climatic changes as inferred from meteorological data and surface hydrological changes related to construction of the railroad. The results indicate that cold years with limited snowfall as well as altered drainage patterns associated with infrastructure development may have contributed to the recent palsa formation.

This study presents the decay of a small palsa complex between 1996 and 2000 in Sweden's southernmost major palsa bog. The outline of the palsa was mapped during three summers in 1996, 1999 and 2000 and an automatic weather station measured air temperature, precipitation, snow depth, wind speed and wind direction between 1997 and 2000. The decay of the palsa was enormous in the dome–shaped part of the palsa complex: the height decreased during the observation period from 2.3 m to 0.5 m. In 2000, the palsa dome had almost totally disappeared: only some peat blocks in a palsa pond were left. The decay of the palsa was complex with a number of degradational processes, of which the main processes were block erosion, thermokarst and wind erosion. Thermal melting has occurred along the edges of the palsa and possibly below the frozen core of the palsa since 1998/99. Wind erosion was observed during summer and the maximum estimated deflation was 80 cm. The decay of the palsa dome was especially large between 1999 and 2000, probably due to a high mean annual temperature, high summer precipitation and the warming influence of the large pond surrounding the palsa. The present climate in the palsa bog with a mean annual temperature of −0.8°C is not favourable for palsa development and maintenance, despite a strong wind regime which can provide suitable conditions for snowdrift.

Changes in the distribution of palsas in Sweden's most southerly major palsa bog are outlined from 1960 to 1997 using aerial photographs taken in 1960 and 1976 as well as a study reported in a publication from 1967 and fieldwork in 1996 and 1997. The geomorphological changes are compared with changes in temperature and precipitation. Between 1960 and 1997, there was a decrease of c. 50% in the area of palsas and no new palsas seem to have developed during the period. Temporary new frost mounds developed during a winter with low snow cover (1995–96) but had disappeared again at the start of the field season of 1997. From open sections in selected palsas, samples were selected at levels of vegetational change indicating stages in palsa development. Radiocarbon dates of 95plusmn;65 a BP and 105plusmn;65 a BP give ages for the start of growth of palsas and a date of 390±70 a BP may represent the last active phase of a previous palsa. The results suggest that some presently existing but decaying palsas started their growth possibly as late as during the last part of the Little Ice Age. It is suggested that the present decay of palsas could be the result of the 1–1.5 °C increase in mean annual temperature in northern Sweden during the last c. 100 years, in particular since the 1930s, probably in combination with increased snowfall since c. 1930. Copyright © 2000 John Wiley & Sons, Ltd. Les modifications qui se sont produites de 1960 à 1997 dans la distribution des palses au sein du marais à palses le plus méridional de Suède ont été reconnues en utilisant des photos aériennes prises en 1960 et en 1976, une publication datant de 1967 et des travaux sur le terrain en 1996 et 1997. Les changements géomorphologiques observés sont mis en relation avec les changements de température et de précipitations enregistrés dans la région. Entre 1960 et 1997, le surface totale de palses du secteur a diminué d'environ 50% et aucune nouvelle palse n'est apparue. Des buttes cryogènes temporaires nouvelles se sont développées pendant un hiver où la couverture de neige était faible (1995/96) mais ces buttes sont disparues au début de l'été 1997. A partir de coupes dégagées dans des palses choisies, des échantillons ont été prélevés à des niveaux où des changements de végétation indiquaient des stages dans le développement des palses. Des dates 14 de 95±65 ans BP et 105±65 ans BP représentent l'âge du début de la croissance des palses et une date de 390±70 ans BP pourraient représenter la dernière phase active d'une ancienne palse. Ces résultats suggèrent que quelques palses existant de nos jours (en fusion aujourd'hui) ont probablement commencé leur croissance peut être pendant la dernière partie du petit âge glaciaire. Il est suggéré que la fusion actuelle des palses pourrait résulter d'une augmentation de l à 1.5 °C de la température moyenne annuelle de la Suède septentrionale pendant le dernier siècle, et plus précisément depuis les années 1930, probablement en combinaison avec une augmentation des précipitations neigeuses. Copyright © 2000 John Wiley & Sons, Ltd.

Pollen stratigraphy of an extrazonal palsa bog in the middle taiga of the West Siberian Plain is dated by radiocarbon at five levels. Local pollen assemblage zones (LPAZ) are the basis for palaeogeographical reconstructions. Tundra-steppe plant communities with shrub birch ( Betula nana) dominated in the latest Pleistocene. Warming after 10 000 14C yr BP caused the local thawing of permafrost, forming shallow lakes. Larixand then Picea spread along river valleys and depressions. Steppe plant communities existed on the dry interfluves. Further climatic warming and drying caused Picea to retreat, and Betula forest-steppe dominated 9500–8900 yr BP. Dense Pinus sylvestris and Pinus sibirica forests then spread over the whole area, and steppe communities decreased about 8300 yr BP. The Holocene climatic optimum (6000–5000 yr BP) was characterized by warm and wet conditions and Abies was widespread. Cooling then caused retreat of Abiesforests to the south and the expansion of Pinus sibirica forests on clay soils and Pinus sylvestris forests on sandy soils. Cooling about 4300 yr BP caused the peat to freeze and the palsa to form by bulging. Peat accumulation on the Bugristoye bog stopped at this time.

In addition to air temperature, snow cover, vegetation cover and superficial deposits are very impor-tant factors affecting the ground thermal regime in the alpine zone. Ground temperatures to a depth of 100cm were measured in the alpine zone of the Daisetsuzan Moun-tains in the autumn of 1993. The alpine zone is a periglacial environment and is occupied by the Pinus pumila community, Sasa kurilensis community, alpine tall herbaceous community, wind-blown plant community and peat land. Higher ground temperatures were recorded in the alpine tall herbaceous community and Sasa kuril-ensis community, where the ground surfaces are covered with more than 100 cm of snow in winter. The snow cover protects the ground from heat loss because of its very low thermal conductivity. In summer, vegetation cover does not play an equivalent role as an insulator. Consequently the ground temperatures in autumn are comparatively high. The snow depth in the Pinus pumila community exceeds 100 cm as well. However, the autumn ground temperature in the community is the lowest except for that in the permafrost area. The low ground temperature is probably caused by the vegetational condition of the Pinus pumila communi-ty, which is distinctive in the summer alpine zone. The dense vegetation canopy of the Pinus pumila community considerably reduces the solar radiation reaching the ground surface. Additionally, the evap-oration from the leaves has a cooling effect in the Pinus pumila community. Since Pinus pumila communi-ty, characterizing the alpine zone of Japan, creates a peculiar environment for the ground thermal regime, the significant effect of the community has to be well taken into consideration when the periglacial environment is studied there. The surface thermal regime in wind-blown bare ground is directly influenced by the fluctuation of air temperature and solar radiation. In the study area, the ground surface temperature falls below -20°C in winter and rises higher in summer than in the ground under other surface conditions. As a result, the temperature of the wind-blown bare ground in the Daisetsuzan Mountains is comparative-ly high in autumn. Permafrost, however, occurs in the bare ground in areas such as Hokkaidaira where the surface layer has a loose structure composed of uncompressed deposits of pumice and scoria. The ground thermal conditions in winter are not very different from that of other sandy and grav-elly bare ground. But in summer, the heat conductivity of the surface layer is lower, since the layer?under dry conditions contains a great deal of air. Water content is a very significant controlling factor for the ground temperature in peat land. Higher ground temperature was recorded in autumn in the low peat land, where the peat layer was sat-urated with water and had high thermal conductivity. In contrast, in a palsa bog, whose surface is 80 cm above the ground water level, permafrost is protected by a dry peat layer more than 60cm thick with very low thermal conductivity. Organic layers, such as humus layer and lichen mat, have relatively low thermal conductivity under dry conditions as well. In the wind-blown ground of the study area, when the organic layer is more than 30 cm thick and, moreover, is underlain by a silty layer with plant remains, the ground ther-mal condition is similar to that of palsa. Consequently, permafrost may occur there.

In the central highland of Iceland, the creation of a small lake partly flooded a dried-up palsa bog. The palsas upshore experienced raised summer soilwater levels and inundation during winter. The effects of these changed hydrological conditions on 5 palsas were monitored over a period of 5 years. All the palsas increased in height, from 14 to 43 cm, with a mean of 27 cm. A core through one palsa showed that while it was formed by segregation ice, the observed height increases were caused by the addition of a layer of pure ice.

During the past 100 years, palsa bogs located on the eastern coast of Hudson Bay have undergone major changes associated with global climatic warming of the northern hemisphere. The recent main developmental stages of palsas, collapse scars, and thermokarstic pools were reconstructed within a representative permafrost peatland located in the southern part of the forest–tundra, using detailed mapping and tree-ring analyses. Maps of the peatland in 1957, 1973, and 1983 indicate a 49% decrease of the total cover of palsas and collapse scars between 1957 and 1983 and a 44% increase of the thermokarstic pool surface. Degradation of the palsa bog was more pronounced between 1957 and 1973 than between 1973 and 1983. Tree-ring analysis of reaction wood on black spruce (Picea mariana (Mill.) BSP.) exposed to unstable peat substratum indicates that permafrost degradation, which began as early as 1880, increased markedly between 1930 and 1965. During the 19th century, the permafrost peatland was mainly composed of large peat plateaus, which subsequently disintegrated into residual palsas, collapse scars, and thermokarstic pools. In addition the increase in temperature during the 20th century, it seems that milder winters with heavier snowfalls promoted conditions conducive to permafrost degradation. The constantly increasing contrast in the microtopographic pattern of the peatland, resulting from the transformation of peat plateaus into smaller palsa units, created more snow cover on east and southeast palsa slopes, thus accelerating permafrost degradation. This autocatalytic process seems to have also played a role in some sections of the peatland with abundant thermokarstic pools, where major changes in drainage conditions have stimulated thermokarstic erosion.